Method for checking the quality of servo gray codes

Abstract

A dynamic threshold detector for a servo writer / detector in a magnetic storage system with a magnetic medium comprises a detector that receives data from the magnetic medium and that selects one of a first condition and a second condition based on at least one of an amplitude, a sign and bit transitions of the data. A threshold selector selects a first set of thresholds when the first condition is selected by the detector and a second set of thresholds when the second condition is selected by the detector. The data includes pairs of numbers with a first number and a a second number each having one of a positive sign and a negative sign and wherein the detector selects the first condition when the signs of the pairs are the same and the second condition when the signs of the pairs are different.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 410,016, filed on Sep. 10, 2002, which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates to magnetic storage systems, and more particularly to digital coding techniques used in magnetic storage systems.BACKGROUND OF THE INVENTION[0003]Magnetic storage systems such as hard disk drives are used to store data. The hard disk drives include one or more platters with an outer magnetic coating. The magnetic coating stores positive and negative magnetic fields that represent binary 1's and 0's. The platters are divided into concentric circles called tracks. The tracks are divided radially into sectors.[0004]When the hard disk drives are manufactured, a servo writer / detector writes permanent servo wedges onto the platters between the sectors. The servo wedges contain data that is used by a read / write head to locate...

AI Technical Summary

Benefits of technology

[0010]In other features, a threshold comparator compares a selected one of the first and second sets of thresholds to the pairs of numbers to detect poor receiving quality. The first set of thresholds includes a first upper threshold and a first lower threshold. The second set of thresholds includes a second upper threshold and a second lower threshold.

[0011]In still other features, the pairs of numbers are generated by a Viterbi detector that sums adjacent numbers in a received string. The first upper threshold i

Problems solved by technology

A bad quality sample is declared when a sample in the new string of numbers is within a predetermined threshold.

However, the predetermined threshold does not adequately determine the readback quality of the detected Gray code.

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